LeetCode Online Judge 题目C# 练习 - Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.

For example,

Given 1->2->3->3->4->4->5, return 1->2->5.

Given 1->1->1->2->3, return 2->3.

 1         public static LinkedListNode RemoveDuplicatesfromSortedListIIOpt(LinkedListNode head)
 2         {
 3             if (head == null || head.Next == null)
 4                 return head;
 5 
 6             LinkedListNode fakeHead = new LinkedListNode();
 7             LinkedListNode prev = fakeHead;
 8             prev.Next = head;
 9             LinkedListNode curr = head;
10 
11             while (curr != null && curr.Next != null)
12             {
13                 //curr Node has duplicated
14                 if ((int)curr.Value == (int)curr.Next.Value)
15                 {
16                     //find the next Node, which value != curr.value
17                     int temp = (int)curr.Value;
18                     curr = curr.Next;
19                     while (curr != null && (int)curr.Value == temp)
20                     {
21                         curr = curr.Next;
22                     }
23                     prev.Next = curr;
24                 }
25                 //curr Node has no duplicated
26                 else
27                 {
28                     prev = prev.Next;
29                     curr = curr.Next;
30                 }
31             }
32 
33             return fakeHead.Next;
34         }

代码分析：

　　这一题稍稍有点tricky。我还是创建了一个fakeNode，用来连接head，返回的时候返回fakeHead.Next, 这样下面的逻辑就适合所有的Node了，而不用去特殊处理第一个Node就有duplicate 的 corner case。

　　这种题虽然是BF，没什么好复习的，但是还是要小心再小心，不容易写出BUG FREE的CODE。